The present invention relates to a catheter for insertion into bodily vessels and an accompanying method. More particularly, the invention relates to a method and an apparatus for catheter insertion over guide wires of different diameters.
In many instances of patient treatment, it is necessary to implant a vascular prosthesis (stent) into the human vasculature in an effort to maintain the patency of the vessel. Stents are typically implanted by use of a catheter which is inserted into the human vasculature at an easily accessible location and then advanced through the vasculature to the deployment site.
One type of catheter used to deliver a stent to the target location is a coaxial, over the wire delivery catheter. Typically, such a delivery catheter is formed with an inner guide wire lumen which is configured to be passed over a guide wire of a particular size. Though it is possible to utilize a catheter having an inner lumen designed for use with a large diameter guide wire with a smaller diameter guide wire, the result is not desirable.
The first problem with using a catheter having an inner lumen designed for use with a large diameter guide wire on a small diameter guide wire relates to what is known as the xe2x80x9csnow plowxe2x80x9d effect. The xe2x80x9csnow plowxe2x80x9d effect occurs due to the gap formed between the inner diameter of the catheter inner lumen and the outer diameter of the small diameter guide wire. As a result, the leading edge of the catheter can be displaced eccentrically to one side relative to the wire thus creating somewhat of a scoop which plows forward upon telescoping of the catheter over the guide wire. Often this causes the leading edge of the catheter to scrape along the delicate inner surfaces of the blood vessel. This xe2x80x9csnow plowxe2x80x9d effect sometimes results in unwanted separation of tissue or plaque as the catheter is maneuvered into position.
The second problem with using a catheter having an inner lumen designed for use with a large diameter guide wire on a small diameter guide wire relates to user control over the movement of the catheter. Because the leading edge of a catheter can shift laterally a considerable distance on a small diameter guide wire, precise control is lost over the distal extremity of the catheter. Such lateral shifting of the catheter on the guide wire can contribute to binding between the catheter and the guide wire, and also may cause irregular frictional resistance to relative longitudinal movement whereby user control is diminished.
One proposed solution to the problem has been to create an array of catheters which differ only in their guide wire lumen diameters to accommodate the various guide wire diameters. However, this presents another problem because the manufacturer is burdened with the task of making separate catheter designs and requiring that customers stock each size. Additionally, customers are burdened with the inconvenience and expense of stocking a multitude of different catheters for different sized guide wires.
A catheter and method of implementation are therefore required that overcome the shortcomings inherent in previously known devices. More specifically, a safe, easily manipulable, and cost-effective catheter is needed that provides the requisite flexibility to be compatible with guide wires of different diameters.
The present invention provides for a catheter which substantially increases safety over prior art catheters and a corresponding method of implementing said catheter. Moreover, the catheter of the present invention is relatively inexpensive to manufacture, trouble-free, reliable, and easy to use. Further, the method provided herein provides a safe and innovative approach to implementing the catheter in a vessel.
As mentioned above, one type of catheter used to deliver the stent to the target location is a coaxial, over the wire delivery catheter. Typically, such a delivery catheter is formed with an inner guide wire lumen designed to be compatible with a standard size guide wire. Standard size guide wires are typically available in four different sizes. Though it is possible to use a catheter having an inner lumen designed for use with a large diameter guide wire with a smaller diameter guide wire, as discussed above, the result is not desirable. Although the present invention catheter system is described in connection with stent delivery catheters, it can be easily adapted to vascular catheters, and to virtually any catheter for access to any bodily conduit.
The present invention substantially improves safety and user manipulability by means of its multi-guide wire compatibility. More specifically, the catheter of the present invention is adjustable to conform closely with a plurality of different diameter guide wires. The close conformance of the catheter with the guide wire ensures a minimal gap between the outer diameter of the guide wire and the catheter inner lumen diameter. This minimized gap allows for enhanced control of relative movement of the catheter and alleviates the xe2x80x9csnow plowxe2x80x9d effect.
Any shifting and flexing of the guide wire while in the catheter inner lumen as allowed by a gap can create a binding effect whereby the device loses its coaxial characteristics thereby making it difficult for the user to accurately control. The catheter of the present invention eliminates such a gap and alleviates the above-mentioned detrimental effects because the user can select the catheter construction to be compatible with the diameter of the guide wire employed. Specifically, the tight conformance between the customized catheter guide wire lumen and the guide wire minimizes the detrimental gap.
The minimized gap between the guide wire and the interior diameter at the distal end of the catheter directly relates to the high degree of safety and user manipulability of the catheter. Minimization of the gap contributes to enhanced control of the catheter as it is advanced along the guide wire defining the path through the vessel lumens of the human vasculature.
In regards to expense, the present invention can reduce costs to the end user because of its multi-guide wire capability. Compared to conventional catheters, which are only appropriately used for one size guide wire, the catheter of the present invention can be used safely with a variety of differently sized guide wires, thus reducing the number of catheters the end users must stock. By reducing the numbers in stock, the costs associated with using the present invention catheter is significantly less than that of conventional catheters.
In order to be compatible with a plurality of guide wires, the catheter of the present invention can be formed in a multi-piece fashion. For example, a preferred embodiment of the present invention is formed from three pieces. In this embodiment, the present invention includes a catheter, an adaptor tube, and a lock.
The catheter is formed similarly to a conventional over-the-wire catheter. In this respect, the catheter of the preferred embodiment includes an inner guide wire lumen having an inner diameter sized to accommodate a larger diameter guide wire in close conformance. The inner diameter of the catheter inner guide wire lumen of the preferred embodiment is approximately 0.035 inch. With this relatively large inner diameter, the catheter is capable of accepting guide wires with diameters of up to 0.035 inch, for example.
It is not, however, optimally sized for use with smaller diameter guide wires. Thus, if a smaller diameter guide wire is used, an eccentric gap is created between a smaller diameter guide wire and the inner diameter of the catheter inner lumen resulting in the xe2x80x9csnow plowxe2x80x9d effect and additionally causing binding between the catheter inner lumen and guide wire, which results in restricted longitudinal shifting and decreased control as mentioned above.
To avoid any potentially adverse effects when using guide wires smaller than 0.035 inch, a preferred embodiment of the present invention includes an adaptor tube to be placed inside the catheter. The inner diameter of this adaptor tube is sized to receive, in close conformance, a smaller diameter guide wire. In this regard, a plurality of adaptor tubes can be kept on hand to accommodate a variety of guide wires of varying diameters. With this option, the present invention customizable catheter can be used with a variety of different guide wires.
In order to secure the adaptor tube to the catheter, close conformance between the two is helpful. Additionally, end cap locking means are provided to secure the adaptor tube to the catheter. The end cap locking means may be any one of a number of conventional couplings or locks, such as threaded brakes, snap fittings, press fittings, or bayonet style fittings.
During use, a patient""s vascular system may be accessed, via a convenient location such as the femoral artery, with a large or small diameter guide wire in accordance with well known and established procedures. Thereafter, the physician selects the appropriate catheter with or without an adaptor tube to be telescoped over the guide wire to maintain a guiding relationship at the distal extremity. The physician then slides the appropriately sized catheter over the guide wire to the desired location within the human vasculature.
As seen by the preferred embodiment mentioned above, the catheter of the present invention is relatively inexpensive to manufacture along with being safe and controllable because of its variable, customizable construction.